Torque transfer unit with sealed one way clutch for an engine starting system

ABSTRACT

A starting system for an internal combustion engine includes a pinion gear selectively driven by a starter motor, a drive plate having a set of teeth in constant meshed engagement with the pinion gear and a one-way clutch adapted to interconnect the drive plate and an engine crankshaft. The clutch assembly includes an inner race adapted to be fixed for rotation with the crankshaft. An outer race is fixed for rotation with the drive plate and has circumferentially spaced apart cam surfaces. The clutch also includes a cage for positioning rollers in circumferentially spaced apart alignment with the cam surfaces. A pair of seal plates are coupled to one of the inner race and the outer race. Each seal plate is positioned proximate to and spaced apart from the other of the inner race and the outer race.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/096,939, filed on Sep. 15, 2008. The entire disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure generally relates to a torque transfer mechanismincluding an overrunning roller clutch for selectively transferringtorque between two rotatable components. More particularly, a startingsystem for an internal combustion engine including an overrunning rollerclutch is disclosed.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Hybrid vehicles having an internal combustion engine as a first sourceof motive power and an electric motor as a second source of motive powerhave become increasingly popular based on fuel costs and environmentalconcerns. In at least one hybrid vehicle, the internal combustion engineis frequently started and stopped to most efficiently operate thevehicle. To minimize and/or eliminate noise, vibration and harshnessassociated with typical internal combustion engine starting systems, astarter motor gear may be positioned in constant meshed engagement witha rotating member of the internal combustion engine. A clutch ispositioned along this power path to allow temporary drivinginterconnection between the starter motor and the internal combustionengine. While various clutch designs may be incorporated, cost, size,weight, lubrication requirements and torque carrying capacity concernsexist.

At least one known clutch associated with an automotive vehicle ispositioned immediately adjacent to or partially within the engine blockof the internal combustion engine. This positioning is required becauselubricant within the engine block is provided to the clutch as well.While such an arrangement may prove to be beneficial, the positioning ofthe clutch in this system is limited and is not necessarily desirable.Furthermore, additional special machining may be required to the engineblock or other internal combustion engine components in order to provideappropriate passageways for the lubricant to reach and return from theclutch.

Other known clutch characteristics such as the generation of heat and aloss of efficiency when operating in an overrunning mode may not lendthemselves for use in a vehicle attempting to maximize energyefficiency. Accordingly, it may be desirable to provide an improvedinternal combustion engine starting system having a torque transfermechanism including an improved one-way clutch.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

A starting system for a hybrid vehicle includes an internal combustionengine having a crankshaft rotatably supported within an engine block.The starting system includes a starter motor, a pinion gear selectivelydriven by the starter motor, a drive plate having a set of teeth inconstant meshed engagement with the pinion gear and a sealed one-wayclutch assembly adapted to selectively drivingly interconnect the driveplate and the crankshaft. The clutch assembly includes an inner raceadapted to be fixed for rotation with the crankshaft. An outer race isfixed for rotation with the drive plate and has circumferentially spacedapart cam surfaces. Rollers elements are positioned radiallytherebetween. The clutch assembly also includes a cage for positioningthe rollers in circumferentially spaced apart alignment with the camsurfaces. A pair of seal plates are fixed for rotation with one of theinner race and the outer race and are spaced apart from one another withthe roller elements therebetween. Each seal plate is positionedproximate to and spaced apart from the other of the inner race and theouter race.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic of an exemplary hybrid vehicle equipped with asealed high capacity overrunning roller clutch;

FIG. 2 is a fragmentary cross-sectional view depicting an internalcombustion engine starting system including a sealed high capacityoverrunning roller clutch;

FIG. 3 is an exploded perspective view of a roller clutch and driveplate assembly;

FIG. 4 is a plan view of a roller clutch and drive plate assembly;

FIG. 5 is a fragmentary sectional view of a portion of the startingsystem;

FIG. 6 is a fragmentary sectional view of the roller clutch assembly ina free-wheeling mode of operation;

FIG. 7 is a fragmentary perspective view of another portion of theroller clutch;

FIG. 8 is a perspective view of a portion of an alternate roller clutch;

FIG. 9 is a fragmentary exploded perspective view of a portion of thealternate clutch of FIG. 8;

FIG. 10 is a fragmentary sectional view of the roller clutch assembly ofFIG. 6 in a torque transferring mode of operation;

FIG. 11 is a fragmentary cross-sectional view depicting a portion of analternate internal combustion engine starting system;

FIG. 12 is a fragmentary cross-sectional view depicting a portion of analternate internal combustion engine starting system;

FIG. 13 is a fragmentary cross-sectional view depicting a portion of analternate internal combustion engine starting system;

FIG. 14 is a fragmentary cross-sectional view depicting a portion of analternate internal combustion engine starting system;

FIG. 15 is a fragmentary cross-sectional view of an alternate clutchequipped with a cap and a shoe;

FIG. 16 is a fragmentary perspective view of an alternate cage androller subassembly;

FIG. 17 is a fragmentary sectional view of the cage and roller assemblyshown in FIG. 16; and

FIG. 18 is an exploded perspective view of an alternate drive plateassembly.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

FIGS. 1-7 depict a torque transfer system 8 including a sealed for lifeone-way overrunning clutch 10 arranged to selectively transfer torquebetween rotatable components within an exemplary vehicle 12. Vehicle 12may be configured as a hybrid vehicle having an internal combustionengine 14 as a first source of motive power. A second source of motivepower is provided by an electric motor 16. The schematic of FIG. 1depicts a pair of driven wheels 18, in receipt of torque provided byinternal combustion engine 14 and transferred through a transmission 22.Electric motor 16 is shown in driving communication with another pair ofdriven wheels 24, 26. One skilled in the art will appreciate that thenumber of wheels driven by internal combustion engine 14 or electricmotor 16 is merely exemplary and that any number of other powertransmission arrangements may be implemented including a series hybriddrive, a parallel hybrid drive, or a series/parallel hybrid drive.Alternatively, the vehicle equipped with overrunning clutch 10 need notbe a hybrid vehicle but may be solely equipped with an internalcombustion engine power source.

During operation of vehicle 12, it is contemplated that internalcombustion engine 14 will frequently be stopped and re-started in anattempt to improve fuel efficiency. For example, internal combustionengine 14 may be stopped once a controller 28 determines that thevehicle speed has been below a predetermined threshold for apredetermined amount of time such as when the vehicle is idling at astop light. Depending on a number of inputs to controller 28, such as athrottle position, vehicle 12 may be propelled solely through powerprovided by electric motor 16, power provided by both internalcombustion engine 14 and electric motor 16 or power provided solely byinternal combustion engine 14. Regardless of the control schemeutilized, engine 14 may require frequent restarting.

Torque transfer mechanism 8 includes a starter motor 30 selectivelyoperable to transfer torque to a crankshaft 32 of engine 14 whencontroller 28 signals for a starting or re-starting of internalcombustion engine 14. Starter motor 30 includes a pinion gear 34 inconstant meshed engagement with a ring gear 36 fixed to a drive plate38. Ring gear 36 may be formed as one-piece with drive plate 38 or maybe a separate component fixed for rotation thereto. Drive plate 38includes a central aperture 40 in receipt of a portion of clutch 10.Clutch 10 selectively transfers torque between drive plate 38 andcrankshaft 32. A flex plate 42 is fixed for rotation with a torqueconverter 44 by a plurality of fasteners 45. Torque converter 44 issupported for rotation within transmission 22. Flex plate 42 is alsofixed for rotation with crankshaft 32 as described below.

Clutch 10 includes an outer race 46 fixed for rotation with drive plate38, an inner race 48 fixed for rotation with crankshaft 32, a pluralityof rollers 50, a cage 52, a plurality of roller springs 54, inner andouter plates 55, 56, inner and outer snap rings 57, 58, a plurality ofaccordion springs 59 and an ID-OD clip 60. Crankshaft 32 is supportedfor rotation within an engine block 62 by a plurality of bearings (notshown). A block seal 66 is seated within a bore 68 formed within a sealcover 70 fixed to engine block 62. Seal cover 70 includes a peripherallip 72 in receipt of a bushing 74. Outer race 46 is supported forrotation by bushing 74. ID-OD clip 60 restricts axial movement of outerrace 46 relative to seal cover 70.

A pilot portion 76 of outer race 46 is positioned within aperture 40 ofdrive plate 38. Pilot portion 76 may be coupled to drive plate 38 in apress-fit arrangement where an inner surface 78 of drive plate 38 ispositioned in abutment with a stepped seat 80 of outer race 46. Moreparticularly, drive plate 38 may be press-fit and microsplined to outerrace 46. Alternatively, drive plate 38 and outer race 46 may be welded.An inner diameter of outer race 46 includes an inner ring groove 82, anouter ring groove 84 and a plurality of cam surfaces 86. Each of grooves82, 84 has a substantially cylindrical shape. Cam surfaces 86 arecircumferentially spaced apart from another with each cam surface 86having a shallow end 92 and a deep end 94 further radially recessed intoouter race 46.

Inner race 48 includes a substantially circular cylindrical mountingflange 96 in engagement with an end face 98 of crankshaft 32. Aspreviously mentioned, inner race 48 is fixed for rotation withcrankshaft 32. In the arrangement depicted in FIG. 2, inner race 48 isfixed to crankshaft 32 with threaded fasteners 99. Fasteners 99 fixinner race 48 and flex plate 42 for rotation with crankshaft 32. Innerrace 48 includes an inner stepped recess 100 and an outer stepped recess102 positioned on either side of a substantially smooth roller contactsurface 104. Each of features 100, 102, 104 include substantiallycylindrically-shaped surfaces.

A roller and cage subassembly 110 includes rollers 50, cage 52 andplurality of roller springs 54. Roller and cage subassembly 110 may besubsequently inserted between outer race 46 and inner race 48.

Cage 52 may be a molded plastic component or constructed from metal andmay be referred to as skeleton 52. Cage 52 includes a first ring 120 anda second ring 122 spaced apart from one another and interconnected by aseries of webs 124 axially extending between first ring 120 and secondring 122. Webs 124 are circumferentially spaced apart from one another apredetermined distance corresponding to a desired position of rollers50. Webs 124 define a plurality of windows 126 within cage 52 to receiverollers 50 as well as roller springs 54 as will be described. Cage 52also includes four radially outwardly extending arms 128 having anaccordion spring 59 coupled thereto.

To assemble roller and cage subassembly 110, rollers 50 are snapped intoplace within opposing sets of roller springs 54. Each roller spring 54includes a guide 130 including bifurcated legs 132 to position one sideof each roller 50 at a desired location. At an end opposite of guide130, roller spring 54 is coupled to cage 52. It should be appreciatedthat two roller springs 54 cooperate with each other to position asingle roller 50.

Roller and cage subassembly 110 may now be positioned between inner race48 and outer race 46. As shown in FIGS. 4 and 6, outer race 46 includesfour circumferentially spaced apart recesses 134. The terminal ends ofarms 128 and accordion springs 59 are positioned within recesses 134.More particularly, one end of accordion spring 59 engages a firstsidewall 136 of recess 134. Arm 128 is biased toward a second opposingsidewall 138. When inner race 48 and outer race 46 are at rest,accordion springs 59 rotate cage 52 to engage arms 128 with secondsidewalls 138. At this cage position, clutch 10 is in an open orfree-wheeling mode where rollers 50 are spaced apart from inner race 48and are located within deep ends 94. This is also the position of cage52 when inner race 48 rotates relative to outer race 46 in a firstdirection such as when internal combustion engine 14 is operating andstarter motor 30 is not operating.

Once roller and cage subassembly 110 is positioned between outer race 46and inner race 48, one axial end of clutch 10 may be enclosed bypositioning inner seal plate 55 in engagement with a seat 137 positionedadjacent to inner ring groove 82. The thickness of inner seal plate 55,inner ring groove 82, and the position of seat 137 cooperate with oneanother such that inner seal plate 55 is fixed for rotation with outerrace 46. An inner circumferential edge of inner seal plate 55 ispositioned proximate to but clear of inner race 48. A lubricant, such asgrease, may be placed in contact with rollers 50, cage 52, rollersprings 54 and inner seal plate 55. The lubricated roller and cagesubassembly 110 may be enclosed by installing outer seal plate 56 andouter snap ring 58. Outer seal plate 56 is fixed for rotation with outerrace 46 in a similar manner to that described in relation to inner sealplate 55. Outer seal plate 56 is positioned in close proximity to butspaced apart from inner race 48 such that frictional losses areminimized and/or eliminated during operation of clutch 10. It isenvisioned that clutch 10 need not be lubricated after initial assembly.Accordingly, clutch 10 is a sealed-for-life component. As previouslymentioned, ID-OD clip 60 restricts clutch 10 from axial movementrelative to internal combustion engine 14. Furthermore, it should beappreciated that seal plates 55, 56 may alternatively be fixed forrotation with inner race 48 and clear of outer race 46.

In another arrangement depicted in FIGS. 8 and 9, roller springs 54 maybe replaced with a one-piece multi-spring 139 including a first rim 140and a second rim 142 axially spaced apart from one another. Each offirst rim 140 and second rim 142 are shaped as split rings having gaps144 formed therein, respectively. A plurality of axially extendingsupports 146 interconnect first rim 140 and second rim 142. Supports 146are circumferentially spaced apart from one another and each include abase portion 148 and a pair of upturned, radially outwardly extending,guides 150. Preferably, first rim 140, second rim 142 and supports 146are integrally formed with one another from one piece of spring steel.Each base portion 148 includes an aperture 152 extending therethrough.Apertures 152 cooperate with radially inwardly extending pegs (notshown) formed on certain predetermined webs 124. Each guide 150 includesa foot portion 154 extending from base portion 148, a lower leg portion156 and an upper leg portion 158. Lower leg portion 156 and upper legportion 158 are substantially planar segments intersecting one anotherat an angle greater than 90° but less than 180°. A trough 160 is formedat the intersection of lower leg portion 156 and upper leg portion 158.

Guides 150 are spaced apart from one another such that pairs of upperedges 162 of upper leg portions 158 are spaced apart a distance lessthan a diameter of roller 50. Pairs of troughs 160 are spaced apart fromone another a distance greater than the diameter of rollers 50.Accordingly, each roller 50 is captured within a pocket 164 betweenguides 150, first rim 140 and second rim 142 and free to rotate therein.Each guide 150 is a resilient member movable from its nominal positionshown in the Figures. Because each guide 150 is individually movable,each roller 50 may be simultaneously engaged with contact surface 104and one of cam surfaces 86 to transfer a maximum quantity of torquethrough clutch 10. The resiliently movable guides 150 allow a somewhatrelaxed tolerancing of the components of clutch 10 while assuring thatthe full complement of rollers 50 transfer torque when required.

Regardless of which roller spring or multi-spring arrangement isimplemented, it may be desirable to frequently start and stop internalcombustion engine 14 during vehicle operation. When internal combustionengine 14 is stopped, neither outer race 46 nor inner race 48 arerotating. Accordion springs 59 biasedly engage arms 128 to urge rollers50 toward deep ends 94 of cam surfaces 86, as shown in FIG. 6. Clutch 10is in the open or free-wheeling mode.

During a starting sequence, clutch 10 operates in the locked or torquetransferring mode as shown in FIG. 10. Starter motor 30 is energized torotate pinion gear 34. Through the meshed interconnection of pinion gear34 and ring gear 36, drive plate 38 and outer race 46 are also rotated.At this time, crankshaft 32 and inner race 48 are not rotating. As such,relative rotation between outer race 46 and inner race 48 occurs urgingrollers 50 toward shallow ends 92 of cam surfaces 86. Rollers 50 arewedged between cam surfaces 86 and roller contact surface 104 totransfer torque between outer race 46 and inner race 48. Accordionsprings 59 are compressed.

Once internal combustion engine 14 has started, starter motor 30 is nolonger energized. As internal combustion engine 14 runs, crankshaft 32and inner race 48 rotate faster than outer race 46 and drive plate 38.Cam surfaces 86 no longer urge rollers 50 toward shallow ends 92. Forceis provided from accordion springs 59 to rotate cage 52 and move rollers50 into the position clear of inner race 48. Relative rotation betweenrollers 50 and outer race 46 does not occur and energy losses due tofriction are avoided.

Lubricated for life overrunning clutch 10 provides a low cost, energyefficient solution for providing high torque capacity within a smallpackaging envelope. As previously mentioned, inner race 48 is fixed tocrankshaft 32 thereby defining an inner diameter of clutch 10. An outerdiameter of clutch 10 is minimized by closely packing as many rollers 50as possible within the circumferential envelope defined by outer race 46and inner race 48. In the example depicted in the figures, forty rollersare utilized. Each roller is substantially cylindrically shaped having adiameter of approximately 4 to 5 mm. The center-to-center distancebetween adjacent rollers is approximately 7.5 mm. As such, the gapbetween each adjacent roller is approximately 2.5 to 3.5 mm or 33 to 50%of the roller diameter. This roller sizing and packing configurationprovides a theoretical high torque output. To assure that the actualtorque capacity of clutch 10 substantially meets the theoretical torquecapacity, roller springs 54 assure that each and every roller 50transfers torque between outer race 46 and inner race 48 when clutch 10operates in the locked mode.

FIG. 11 depicts another torque transfer mechanism 180. Torque transfermechanism 180 is substantially similar to torque transfer mechanism 8previously described. Accordingly, like elements will retain theirpreviously introduced reference numerals including a prime suffix. Tofurther increase the operational efficiency of torque transfer mechanism180, bushing 74′ has been replaced with a bearing assembly 182. Bearingassembly 182 accurately locates and supports outer race 46′ for rotationrelative to engine block 62′. A snap ring 184 axially locates bearingassembly 182 on engine block 62′. Clutch 10′ includes a cage 186 havinga radially inwardly extending flange 188. Cage 186 includes acircumferential groove 190. A similar opposing circumferential groove192 is formed on outer race 46′. One or more ball bearings 194 arepositioned within grooves 190, 192 to guide cage 186 relative to outerrace 46′ and reduce the friction therebetween during relative rotation.It should be appreciated that during the open or free-wheeling mode ofoperation, no frictional losses occur between rollers 50′, inner race48′, outer race 46′ and cage 186.

FIG. 12 depicts another alternate torque transfer mechanism at referencenumeral 200. Torque transfer mechanism 200 illustrates that sealed forlife clutch 10 may be positioned at any number of locations throughoutthe power transfer path because an oil feed from internal combustionengine 14 is not required. In particular, torque transfer mechanism 200depicts clutch 10 connected to a dual mass flywheel or a torqueconverter 202. The dual mass flywheel or torque converter 202 issupported for rotation within a transmission housing 204. Enginecrankshaft 32 is fixed for rotation with dual mass flywheel or torqueconverter 202. Accordingly, starter motor 30 may output a torque to adrive plate 206 that is fixed for rotation with outer race 46. Innerrace 48 is press-fit to and fixed for rotation with dual mass flywheelor torque converter 202. A bushing 208 may be used to locate outer race46 in the radial direction. Therefore, starter motor 30 may drive atransmission component instead of an internal combustion enginecomponent.

FIG. 13 depicts another variation of torque transfer mechanism 200 asidentified as torque transfer mechanism 220. Torque transfer mechanism220 differs from torque transfer mechanism 200 in that bushing 208 hasbeen replaced with a bearing 222.

FIG. 14 depicts another alternate torque transfer mechanism 240. Torquetransfer mechanism 240 is substantially similar to torque transfermechanism 180 except that clutch 10 has been replaced with a dry one-wayclutch 10″. Clutch 10″ is substantially similar to clutch 10 except thata lubricant is not trapped between inner race 48″ and outer race 46″through the use of seal plates similar to those previously described. Onthe contrary, relatively large air gaps exist between seal plates 55″,56″ and inner race 48″. This arrangement assures a very low resistanceto relative rotation between inner race 48″ and outer race 46″ ispresent during the free-wheeling mode of operation.

FIG. 15 depicts another clutch identified at reference numeral 600.Clutch 600 includes an outer race 602 fixed for rotation with a driveplate 604, an inner race 606, rollers 607, a cage 608, a cage retainerplate 610, a seal 612 and an ID-OD clip or seal plate 614. Clutch 600also includes a cap 616 that is coupled to outer race 602 via a shrinkfit process. Accordingly, an inner cylindrical surface 618 of cap 616applies a compressive force to an outer cylindrical surface 620 of outerrace 602. The compressive force offsets a hoop stress occurring in outerrace 602 when clutch 600 is locked.

Furthermore, cap 616 includes a radially inwardly extending flange 622having a substantially planar inner face 624. Planar face 624 engages aface 626 of ID-OD clip 614. ID-OD clip 614 is trapped between flange 622and a land 628 formed on outer race 602. Cap 616 functions to lock ID-ODclip 614 to outer race 602. ID-OD clip 614 is restricted from rotationrelative to outer race 602 during clutch operation.

Clutch 600 also includes a shoe 632 fixed to an inner diameter portion634 of ID-OD clip 614. Shoe 632 includes a “C”-shaped cross sectionhaving a first leg 636 and a second leg 638 interconnected by an endwall 640. Shoe 632 may be formed from bronze, a polymer or some otherfriction reducing guide material. Shoe 632 may be fixed to ID-OD clip614 by a number of methods including mechanical fasteners such as rivetsor via an adhesive. Alternatively, shoe 632 may be overmolded to ID-ODclip 614. In yet another version, shoe 632 may be formed from two pieceswhere the shoe is fixed with a mechanical lock that may separate underload conditions. First leg 636 includes a guide surface 644 spaced apartfrom a side wall 646 of a groove 648 formed in inner race 606.Similarly, second leg 638 includes a guide face 650 spaced apart from anopposite side wall 652 of groove 648.

FIGS. 16 and 17 depict an alternate roller and cage subassembly 660including rollers 662, a cage 664 and a multi-spring 666. Each roller662 is trapped between a concave surface 668 formed on cage 664 and aconvexedly-shaped distal end 670 of multi-spring 666. A body portion 672of multi-spring 666 includes a serpentine shape thereby allowing distalend 670 to deflect during clutch operation. Distal end 670 biases roller662 toward concave surface 668. Roller 662 is positioned in a groove 676formed in an outer race 678.

FIG. 18 depicts an alternate drive plate 700 including a gear 702, a hub704 and an outer race 706. Gear 702 is preferably constructed from ametal such as hardenable steel and includes a plurality of externalteeth 708, as well as a substantially inner cylindrical surface 710. Hub704 includes an inner ring 712, an outer ring 714 and a plurality ofradially extending spokes 716 interconnecting outer ring 714 and innerring 712. Hub 704 is preferably constructed from a lightweight materialsuch as a polymer. Outer race 706 is preferably constructed from a metalsuch as a hardenable steel and is substantially similar to the outerraces previously described. Drive plate 700 may be constructed using aovermolding process where outer race 706 and gear 702 are placed withinan injection mold cavity. Molten resin is injected into the mold cavityto define hub 704 while simultaneously fixing outer ring 714 to gear 702as well as fixing inner ring 712 to outer race 706. The relatively lowweight and low cost drive plate 700 may be used in conjunction with anyof the clutches previously described.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without departing from the spirit and scope of thedisclosure as defined in the following claims.

1. A starting system for a hybrid vehicle including an internalcombustion engine having a crankshaft rotatably supported within anengine block, the starting system comprising: a starter motor; a piniongear selectively driven by the starter motor; a drive plate having a setof teeth in constant meshed engagement with the pinion gear; and aone-way clutch assembly adapted to selectively drivingly interconnectthe drive plate and the crankshaft, the clutch assembly including aninner race adapted to be fixed for rotation with the crankshaft, anouter race fixed for rotation with the drive plate and havingcircumferentially spaced apart cam surfaces, and a plurality of rollerelements positioned radially therebetween, the clutch assembly alsoincluding a cage for positioning the rollers in circumferentially spacedapart alignment with the cam surfaces, the clutch including a pair ofseal plates coupled to one of the inner race and the outer race as wellas being spaced apart from one another with the roller elementstherebetween, each seal plate being positioned proximate to and spacedapart from the other of the inner race and the outer race.
 2. The systemof claim 1 further including snap rings engaging each of the seal platesto couple the seal plates to one of the inner and outer races.
 3. Thesystem of claim 2 wherein the outer race is adapted to be supported forrotation by the engine block.
 4. The system of claim 3 further includinga retaining ring positioned within a ring groove formed on the outerrace to restrict movement of the clutch relative to the engine block. 5.The system of claim 4 further including a bushing adapted to be fixed tothe engine block, the bushing rotatably supporting the outer race. 6.The system of claim 5 further including a bearing adapted to be fixed tothe engine block, the bearing rotatably supporting the outer race. 7.The system of claim 4 wherein the cage includes first and second spacedapart rings interconnected by axially extending webs.
 8. The system ofclaim 4 wherein the retaining ring remains positioned within the ringgroove formed on the outer race at relative rotational speeds betweenthe outer race and the engine block in excess of 6500 RPM.
 9. The systemof claim 1 wherein each roller element has a diameter and adjacentroller elements have a space therebetween less than one roller diameter.10. The system of claim 1 further including a spring acting on the cageto space apart the roller elements from the inner race and place theclutch in a free-wheeling mode.
 11. The system of claim 10 wherein thespring is coupled to an arm radially extending from the cage, the springand arm being positioned within a recess formed in the outer race. 12.The system of claim 11 wherein the spring is compressed and the arm isdisengaged from the outer race when the roller elements engage with thecam surfaces and the inner race to place the clutch in a torquetransferring mode.
 13. The system of claim 11 wherein the arm engagesthe outer race and the cage positions the roller elements in a deepportion of the cam surfaces when the clutch is in the free-wheelingmode.
 14. The system of claim 1 further including grease being containedin contact with the roller elements by the seal plates.
 15. The systemof claim 1 further including a cap including an inner surfacecircumscribing and being biasedly engaged with an outer surface of theouter race.
 16. The system of claim 15 wherein the cap is fixed to theouter race in a shrink fit.
 17. The system of claim 15 wherein the capincludes a flange engaging one of the seal plates to restrict relativerotation between the outer race and one of the seal plates.
 18. Thesystem of claim 1 wherein the drive plate includes a polymeric hub fixedto the outer race, wherein the teeth are formed on a metallic ring fixedto the polymeric hub.